For the past five years we have been investigating techniques to improve vessel visibility in magnetic resonance angiography (MRA). Much of this work has focussed on optimization of time of flight (TOF) techniques. In 1988 we developed the multiple overlapping thin slab 3D acquisition technique (MOTSA) and are currently studying optimization of gradient waveforms in an attempt to achieve the highest possible spatial resolution and visualization of the smallest possible vessel detail. The goal, which remains elusive, is to develop a technique for the consistent visualization of small vessels (on the order of 0.3 mm diameter). In parallel with these studies to optimize image acquisition technique, we have recently discovered that some very basic image processing techniques can be used to significantly enhance small vessel visibility. In this proposal we request support (l) to complete a theoretical and experimental study to explain why these techniques work, (2) to evaluate in clinical studies the extent and consistency of improvement in vascular detail obtained using these techniques, (3) to compare the improvement in vascular detail with that obtained using magnetization transfer, and (4) to investigate others forms of post processing techniques which are logical extensions of the presently implemented algorithms.